Lipotes vexillifer Miller,
English: Yangtse river-dolphin; baiji; whitefin dolphin
German: Chinesischer Flussdelphin
Spanish: Baiji; Delfín de China
French: Baiji; Dauphin de Chine
Lipotes vexillifer © Würtz-Artescienza
The baiji has been the rarest and most endangered cetacean in the
world (Smith et al. 2008); it is currently thought to probably be
extinct (IUCN, 2009). It was a very graceful animal, with a very
long, narrow and slightly upturned beak. The baiji could easily
be identified by the rounded melon, longitudinally oval blowhole,
very small eyes, low triangular dorsal fin and broad, rounded flippers.
The coloration was bluish-grey to grey above and white to ashy-white
below. Females were larger than males, reaching 253 cm as opposed
to 229cm (Zhou, 2002).
The baiji was an exclusively freshwater species and ranged in the
lower and middle reaches of the Chang Jiang (Yangtze River), from
its estuary upstream for 1,600 km as far as the gorges above Yichang
(20m above sea level). At least one record was reported from the
lower Fuchun Jiang at Tonglu (Rice, 1998). Individuals may have
entered some tributary lakes during intense flooding (Zhou, 2002).
Distribution of the possibly extinct Lipotes
vexilifer in the Chang Jiang (Yangtse River) and its
tributaries (Smith et al. 2008 © IUCN; enlarge
3. Population size
Zhou et al. (1998) report that boat surveys conducted along a 500km
section of the Yangtze River between Zhenjiang and Hukou in 1989-1991
resulted in identification of seven individual baiji based on natural
markings. There were 7 sightings of baiji in May 1989, 4 sightings
in March 1990 and 6 sightings in April-May 1990, resulting in an
estimated population size of about 30 individuals in the 500-km
river study area. If the baiji was still inhabiting its historical
1,600 km range in the Yangtse River, and population density was
similar throughout this habitat section, there may have been 100
baiji left in the river at that time.
However, results of subsequent surveys of almost all the species'
previous range, Shanghai to Yichang, suggested that the population
was very small and in further decline. In 1998 only a few dozen
animals may have still been alive (Zhou, 2002). From observations
between 1997-1999, Zhang et al. (2003) concluded that 13 individuals
could be considered as a minimum number of the baiji in the Yangtse
River at that time. The annual rate of population decrease was roughly
estimated as 10%. The distribution range of the baiji was less than
1,400 km in length in the Yangtze main river. Distances between
the two nearest groups of baiji appeared to be increasing.
In Dongting Lake and Boyang Lake, the baiji became extinct by 1999
(Yang et al. 2000). Finally, an intensive six-week multi-vessel
visual and acoustic survey carried out in November-December 2006,
covering the entire historical range of the baiji in the main Yangtze
channel, failed to find any evidence that the species survives (Turvey
et al. 2007). The authors concluded that the baiji is now likely
to be extinct, probably due to unsustainable by-catch in local fisheries.
This represents the first global extinction of a large vertebrate
for over 50 years, only the fourth disappearance of an entire mammal
family since AD 1500, and the first cetacean species to be driven
to extinction by human activity. There are no baiji in either natural
reserves or in dolphinariums (Smith et al. 2008).
4. Biology and Behaviour
Habitat: Baiji were generally found in eddy countercurrents
below meanders and channel convergences. The Yangtze River is turbid,
and visibility from the surface downward is about 25-35cm in April
and 12cm in August. Baiji eyes were correspondingly reduced, much
smaller than those of other dolphins and placed higher on the head.
However, they were functional, and baiji could distinguish objects
placed on the surface (Zhou, 2002). Zhang et al. (2003) reported
that baiji showed a significant attraction to confluences and sand
bars with large eddies.
Schooling: They generally lived in small groups of 3-4 animals,
largest observed group size being 16 animals (Zhou, 2002). Two typical
sightings are described (Zhang et al. 2003), in which surfacing
and movements of baiji were recorded. Baiji were often found swimming
together with finless porpoises. In the surveys they occurred in
the same group in 63% of occurrences.
Behaviour: Baiji would surface without splashing and breathe smoothly.
Short breathing intervals of 10-30s alternated with a longer one
of up to 200s (Zhou, 2002).
Reproduction: The baiji probably bred and gave birth in the
first half of the year. The peak calving season appeared to be February
to April (Zhou, 2002).
Food: Any available species of freshwater fish was taken,
the only selection criterion appears to have been size (Zhou, 2002).
Reyes (1991) classified the species as "non-migratory".
Peixun (1989) reported movements within home ranges but not migratory
behavior. However, baiji also made long-range movements. Hua et
al. (1994) recorded a single individual moving more than 300 km
from March 1989 to January 1992, implying that the baiji's distribution
range may have been dynamic. Anecdotal information from fishermen
in the river during the surveys indicated that baiji moved upstream
when water rose in the spring and downstream when water receded
in winter (Zhang et al. 2003).
Zhou et al. (1998) showed from photographic identifications and
sighting records that baiji groups made both local and long-range
movements. The largest recorded movement of a recognisable baiji
was 200+ km from the initial sighting location.
As summarized by Zhou (2002), the threats faced by the baiji included
river traffic, fishing gear, reduction of fish stocks, and water
pollution. Zhang et al. (2003) added to this list illegal electrical
fishing, accounting for 40% of known mortality during the 1990s,
and engineering explosions for maintaining navigation channels,
which became another main cause of baiji deaths.
Furthermore the Yangtze was suffering massive habitat degradation
that likely added to the onset of the baiji's demise:
- The banks of the river have been modified extensively to prevent
destructive flooding of agricultural areas, thus reducing the floodplain
area (Zhou, 2002).
- Wastewater volume discharged into the Yangtze is about 15.6 billion
cubic meters per year. Approximately 80% of these wastewaters are
discharged directly into the environment without treatment (Zhou,
- Dudgeon (1995) reported that in the Zhujiang, dam construction
has caused reductions in fisheries stocks but here, as elsewhere
in China, the ecologically damaging consequences of river regulation
are exacerbated by overfishing and increasing pollution of rivers
by sewage, pesticides and industrial wastes. o In addition, deforestation
and soil erosion in the Chang Jiang basin have given rise to siltation
and degradation of floodplain habitats (Dudgeon, 1995).
Finally, Rosel and Reeves (2000) pointed out another, equally threatening
effect. These animals faced an additional suite of potentially serious
problems that were often overlooked, perhaps because they were not
so obvious. The genetic and demographic consequences associated
with very small population size can result in extinction even when
effective measures are in place to protect the animals and their
habitat. Small populations tend to harbor less genetic variation
than large populations. In addition, small populations are more
strongly affected by processes of genetic drift and inbreeding,
both of which can further reduce genetic variability. Genetically
depauperate populations may have lower fitness, a reduced ability
to adapt to changes in their environment over time, and decreased
evolutionary potential. Finally, small populations may also be more
vulnerable to demographic stochasticity, which can accelerate the
process of extinction. Awareness of the genetic and demographic
consequences of small population size should be integral to planning
for conservation of endangered river cetacean species and populations.
Range state (Smith et al. 2009): China
Huan and Chen reported as early as 1992 that "the distribution
density of baiji in the river section of Ouchikou-Chenglingji (158
kilometres) was gradually diminishing. Its distribution density
in the section under research diminished from 3.67 km/per dolphin
in 1986 to 10.36 km/per dolphin in 1991. The baiji has been listed
as First-Class Animal under the protection of the Chinese Government,
but its population size decreases further and human activities still
severely endanger its existence. With further human exploitation
of the Yangtse River, new key water-control projects will be built.
Hence, a conservation strategy must be adopted to rescue this species."
The IUCN lists the species as "critically endangered and possibly
extinct" (C2a(ii); D). It was a relict species and the only
living representative of the family Lipotidae and met the definition
of a Critically Endangered (CR) species, as it is facing an extremely
high risk of extinction in the wild (Smith et al. 2008).
L. vexilifer is listed in appendices I and II of CITES.
Because it was not an internationally migrating species, it was
not listed by CMS.
· Dudgeon D (1995) River regulation in southern China: Ecological
implications, conservation and environmental management. Regulated
Rivers Research & Management 11(1): 35 - 54
· Hua Y, Gao S, Zhang J. 1994. Population size of baiji and
the analysis of the population decreasing. In Working Paper on Baiji
Population and Habitat Viability Assessment Workshop Report, Zhou
K, Ellis S, Leatherwood S, Bruford M, Seal US (eds), 41-45.
· Huan Y, Chen P (1992) Investigation for impacts of changes
of the lower reach of Gezhou Dam between Yichang and Chenglingji
on the baiji, Lipotes vexillifer vexillifer after its key
water control project founded. J Fish China Shuichan Xuebao. 16(4):
· Peixun (1989) Baiji - Lipotes vexilifer. In: Handbook of
Marine Mammals (Ridgway SH, Harrison SR eds.) Vol. 4: River Dolphins
and the Larger Toothed Whales. Academic Pres, London, pp. 25 - 44.
· Reyes JC (1991) The conservation of small cetaceans: a
review. Report prepared for the Secretariat of the Convention on
the Conservation of Migratory Species of Wild Animals. UNEP / CMS
· Rice DW (1998) Marine mammals of the world: systematics
and distribution. Society for Marine Mammalogy, Special Publication
Number 4 (Wartzok D, Ed.), Lawrence, KS. USA.
· Rosel PE, Reeves RR (2000) Genetic and demographic considerations
for the conservation of Asian river cetaceans. In: Reeves, RR (ed);
Smith, BD (ed); Kasuya, T (ed). Biology and conservation of freshwater
cetaceans in Asia. 23: 144-152
· Smith BD, Zhou K, Wang D, Reeves RR, Barlow J, Taylor BL,
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· Turvey ST, Pitman RL, Taylor BL, Barlow J, Akamatsu T,
Barrett LA, Zhao X, Reeves RR, Stewart BS, Wang K, Wei Z, Zhang
X, Pusser LT, Richlen M, Brandon JR, Wang D (2007) First human-caused
extinction of a cetacean species? Biol Lett 3: 537-540
· Zhang, X, Jiang G, Jiang X, Li Y (2001) Impacts on baiji
and finless porpoise by some projects of preventing and controlling
flood in the Yangtze River, with conservation strategies. Resour
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· Zhou K, Sun J, Gao A, Wuersig B. (1998) Baiji (Lipotes
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· Yang J, Xiao W, Kuang X-A, Wei Z, Liu R-J (2000) Studies
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· Zhang X, Wang A, Liu R, Wei Z, Hua Y, Wang Y, Chen Z, Wang
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Aquatic Conserv: Mar. Freshw. Ecosyst. 13: 51-64
© Boris Culik (2010) Odontocetes.
The toothed whales: "Lipotes vexillifer". UNEP/CMS
Secretariat, Bonn, Germany.http://www.cms.int/small-cetaceans
© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.